TY - JOUR
T1 - Hierarchical Characteristics of Hydrogen-Assisted Crack Growth and Microstructural Strain Evolution in Tempered Martensitic Steels
T2 - Case of Quasi-cleavage Fracture
AU - Chen, Tingshu
AU - Chiba, Takahiro
AU - Koyama, Motomichi
AU - Shibata, Akinobu
AU - Akiyama, Eiji
AU - Takai, Kenichi
N1 - Funding Information:
This work was supported financially by JSPS KAKENHI (JP20H02457) and a research project entitled “Mechanism from incubation period to fracture in hydrogen embrittlement of high-strength steels” and funded by the Iron and Steel Institute of Japan (ISIJ).
Publisher Copyright:
© 2021, The Minerals, Metals & Materials Society and ASM International.
PY - 2021/10
Y1 - 2021/10
N2 - The local plastic strain evolution associated with crack growth in hydrogen-assisted quasi-cleavage fracture was investigated using tempered lath martensitic steels. The quasi-cleavage crack grew via the following process. After crack initiation, the crack grew sharply to a certain length by repeated episodes of nano-void nucleation and coalescence. When the sharp crack tip intersected microstructural boundaries such as a lath or block, crack deflection/branching occurred. This was followed by crack tip blunting, which temporarily stopped crack growth. Further crack growth was possible via one of the following two routes: (1) sharp crack initiation/growth from the blunt crack tip, and (2) new crack initiation near the blunt crack tip. The newly formed cracks subsequently coalesced. Repetition of this multi-scale crack growth mechanism finally caused a quasi-cleavage fracture. Correspondingly, hierarchical crack morphologies were observed, which coincided with the lath martensitic microstructures and fractographic features. Furthermore, specific correlations were found between hydrogen-assisted cracking behavior and local plastic strain evolution at different spatial scales. Specifically, the largest plastic strain evolution occurred in the region where crack coalescence was observed. The second largest plastic strain evolution occurred when crack tip blunting occurred. Nanoscale local plasticity evolution around a sharp crack was also observed as an appearance of intense slip bands, indicating that the local plasticity played a key role in the hydrogen-related sharp crack growth.
AB - The local plastic strain evolution associated with crack growth in hydrogen-assisted quasi-cleavage fracture was investigated using tempered lath martensitic steels. The quasi-cleavage crack grew via the following process. After crack initiation, the crack grew sharply to a certain length by repeated episodes of nano-void nucleation and coalescence. When the sharp crack tip intersected microstructural boundaries such as a lath or block, crack deflection/branching occurred. This was followed by crack tip blunting, which temporarily stopped crack growth. Further crack growth was possible via one of the following two routes: (1) sharp crack initiation/growth from the blunt crack tip, and (2) new crack initiation near the blunt crack tip. The newly formed cracks subsequently coalesced. Repetition of this multi-scale crack growth mechanism finally caused a quasi-cleavage fracture. Correspondingly, hierarchical crack morphologies were observed, which coincided with the lath martensitic microstructures and fractographic features. Furthermore, specific correlations were found between hydrogen-assisted cracking behavior and local plastic strain evolution at different spatial scales. Specifically, the largest plastic strain evolution occurred in the region where crack coalescence was observed. The second largest plastic strain evolution occurred when crack tip blunting occurred. Nanoscale local plasticity evolution around a sharp crack was also observed as an appearance of intense slip bands, indicating that the local plasticity played a key role in the hydrogen-related sharp crack growth.
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U2 - 10.1007/s11661-021-06423-1
DO - 10.1007/s11661-021-06423-1
M3 - Article
AN - SCOPUS:85112752659
VL - 52
SP - 4703
EP - 4713
JO - Metallurgical Transactions A (Physical Metallurgy and Materials Science)
JF - Metallurgical Transactions A (Physical Metallurgy and Materials Science)
SN - 1073-5623
IS - 10
ER -